They are only assigned to players who have progressed in Olaf's Quest to the point where they need to enter the Brine Rat Cavern. Alternatively, they can be killed as an alternative for a ratslayer assignment provided the player has the appropriate Slayer level to do so.

Brine rats have relatively low defence, but fairly high strength and attack. As such, it is recommended to bring food if players do not have high (~70) Defence.

Brine rats frequently drop raw swordfish and raw sharks in addition to raw rat meat, so bringing a tinderbox and a couple of logs may be advisable. Alternatively, Olaf, outside the caverns, has a permanent fire located beside him, so players can collect the unnoted raw fish/rat meat drops and cook them on his fire if they are willing to exit and re-enter the caverns multiple times.

Although it looks like safe spots, the bones and skeletons in the area do not work as such.